1. Field of the Invention
This invention relates to pressure sensors, and more particularly to the packaging of pressure sensors so as to eliminate or minimize deleterious ambient and environmental effects.
2. Description of the Prior Art
Small aneroid pressure sensors of the type having a capacitive pressure capsule are well known in the art. For example, one may refer to my U.S. Letters Pat. Nos. 3,808,480, granted Apr. 30, 1974, and 3,880,009, granted Apr. 29, 1975, both assigned to Bunker Ramo Corporation, for discussions of the basic structure and operation of capacitive type pressure capsules. In the latter of these patents, it is explained that variations in pressure can be employed to change the capacitance of an appropriate constructed sensing device in which one of the plates is constructed in the form of a diaphragm. With one side of the diaphragm exposed to a pressure to be sensed, variations in that pressure will be reflected as changes in the capacitance between the diaphragm and a fixed capacitor plate.
As also set forth in that patent, a change in capacitance may be utilized to change the operating frequency of an oscillating circuit or a variable frequency signal generated can be applied to a discriminator to obtain an analog output, or to a gated counter to obtain a digital output. Circuits for accomplishing these functions are disclosed in my aforementioned U.S. Pat. Nos. 3,808,480, and in 3,295,360 and 3,595,084.
The pressure capsule per se and the electronic circuits per se for utilizing a pressure capsule to provide various output signals are not a part of the present invention, but are fully incorporated herein by the above references for a more complete appreciation of the present invention and to simplify the detailed description of the invention.
Heretofore, as evidenced by the above-cited patents, the art has been directed to refining pressure sensors in respect of size and weight reduction, manufacturing economy, and the like. In my U.S. Pat. No. 3,808,480, I also provided for a shielding of an integrated circuit device against electromagnetic interference by placing the integrated circuit between the metallic diaphragms of the pressure capsule.